The sun has erupted with another X-class solar flare, adding a fourth huge solar explosion to the 48-hour tally. Since late Sunday night an X1.7, X2.8, X3.2 and, this morning, an X1.0 flare erupted from the same active region in the lower atmosphere of our nearest star.
These eruptions are triggered by intense magnetic fields upwelling from the sun’s interior. Often associated with complex dark blemishes known as sunspots, these active regions are a symptom of the sun’s inner turmoil as it reaches the apex of its 11-year cycle. 2013 is the predicted peak year of this cycle, known as “solar maximum.”
During this tumultuous time, the sun’s magnetic field is at its most stressed, increasing the likelihood of solar flares, coronal mass ejections (CMEs) and powerful solar winds. Collectively, these phenomena and their impact on the solar system are known as “space weather.” NASA, ESA, NOAA and other nation’s agencies have space observatories that monitor the sun in an effort to predict space weather and, with the help of a multitude of ground-based observatories, the impact of space weather can be measured.
So far, active region (AR) 1748 has been directing its solar flare energy away from Earth, but it is slowly rotating ominously in our direction. NOAA space weather forecasters predict there is an 80 percent chance of more M-class (medium energy) flares and a 50 percent chance of further X-class flares from the same region over the next 24 hours. This activity will likely continue for several days. Should we be getting worried?
The thing with space weather is that we are getting very good at understanding the magnetic triggers deep inside the solar corona, but their effects on our planet can be difficult to predict.
X-class solar flares are the most powerful type of solar flare and their power output is categorized on a linear scale. So, for example, an X2 flare is twice as powerful as an X1 flare. Therefore, the most powerful flare of the past 48 hours — the whopping X3.2 flare on Monday night — is over three times more powerful than today’s X1.0 flare.
Generating ionizing X-ray radiation, these flares can have a dramatic impact on Earth’s upper atmosphere. The upper layers of our atmosphere, the ionosphere, is utilized in the transmission of radio waves around the planet. But as the sun kicks out powerful X-rays, they get absorbed by the ionosphere, modifying its ionized state. This disruption is known as a Sudden Ionospheric Disturbance (or SID for short) and can severely hinder or completely interrupt communications between satellites (such as the GPS network) and the ground. Immediate concern will often focus on air traffic control where the requirement for rapid communications is paramount.
In addition to waves of ionospheric disturbances washing around our planet, periods of high solar activity can have a heating effect on the upper atmosphere, causing atmospheric gases to expand into orbital altitudes. This can have the undesirable effect of increasing drag on satellites and other orbiting bodies, potentially causing them to de-orbit.
And, of course, you don’t really want to be a spacewalking astronaut during intense X-flare activity.
But a far more disruptive space weather phenomenon is the coronal mass ejection (CME).
CMEs can be associated with, but not exclusive to, active flaring regions on the sun.
Take AR 1748 for example: The active region has generated CMEs but all have been fired into deep space, missing all the planets — NASA’s Spitzer space telescope and Epoxi probe, however, will likely be in the path of at least one of these CMEs. CMEs are vast bubbles of magnetized plasma that are launched from the lower corona and accelerated into the solar system. Whereas solar flares transmit energy at the speed of light (as soon a the flare is triggered, the light from the flare hits us within minutes), CMEs travel much slower, typically taking a few days to travel from the sun to Earth. During intense solar activity, however, CMEs can plow through interplanetary space at an astonishing rate, taking just hours to reach the orbit of Earth. But fortunately, these events are rare.
Regardless, CMEs are widely regarded as the menace of space weather as they pack quite an energetic punch.
Should the CME be aligned just right with the magnetic field of the Earth, the magnetic configuration could facilitate the injection of high-energy solar particles deep into our planet’s magnetosphere. This is known as a geomagnetic storm. Sure, there’s a beautiful side effect from this — stunning, glowing aurorae at high latitudes when solar particles interact with the Earth’s atmospheric gases — but there can be dramatic consequences too.
We live in a high-technology civilization, and the sudden injection of high energy particles into the magnetosphere can induce a massive current through the atmosphere. And this current can, effectively, short-circuit power grids, overload substations and plunge entire regions of the globe into a blackout. The secondary impacts then become obvious — what if the geomagnetic storm hits during the winter? Prolonged power outages could turn deadly for the population affected.
These events aren’t without precedent either. In recent history, the worst geomagnetic storm-induced power outage knocked out the HydroQuebec grid in March 1989 — an unexpected surge in electricity knocked out a substation and 6 million people were left without power for several hours. This was only a taster for what the sun can do.
The most famous geomagnetic storm, however, was the “Carrington Event” in 1859. Observing the sun from his UK-based observatory, amateur astronomer Richard Carrington spotted a huge flash on the sun’s surface. Within hours, the CME that powerful flare generated slammed into the Earth’s magnetosphere. Telegraph operators were electrocuted by the surge in electricity along telegraph wires and small fires were sparked. Just imagine the impact such a storm would have on a planet wrapped in communications and electricity cables!
Time to Worry?
Fortunately for us, the current solar cycle is “below average,” so anything like the historic Carrington Event is highly unlikely. Also, we are acutely aware of the sun’s impact on our way of life, so electricity companies have safeguards in place that can reduce the risk of another Quebec-like event. Satellite operators also have contingency plans for flares and CMEs — although, often, there is little that can be done for a satellite that gets whacked by a wave of solar radiation. To top it all off, we have a growing knowledge of our nearest star and we are developing sophisticated prediction models that can forecast how active regions of the sun may evolve.
Living within the atmosphere of a star and coping with explosive events from that hot ball of plasma is something we can’t avoid. We will be hit by powerful flares and CMEs and our technology will suffer. But this is a civilization-wide problem, not necessarily something we, as individuals, can do much about.
So, unless you’re an astronaut working on the outside of the International Space Station, don’t fear space weather. We are protected by a thick atmosphere and powerful magnetic field that absorbs and deflects the worst radiation the sun can throw at us — it’s the health of our satellites, global communications and, very occasionally, national power grids that are most at risk.
So, for now, sit back and enjoy our incredible dynamic sun, but keep in mind that it has no regard for our technological civilization.
Image: Today’s X1.0 solar flare as imaged by NASA’s Solar Dynamics Observatory (SDO) through four of its filters, resolving different plasma temperatures. Credit: NASA/SDO